This invention relates to forms used to define the edges of a concrete platform, slab or the like, and which are generally removed after the concrete has set.
Traditionally, to define a perimeter of a given area to be poured with concrete, a xe2x80x9cform boardxe2x80x9d or perimeter-stopping system using temporary forms is installed. One such temporary form is made of two inch thick (lumber dimension) boards. the widths of which correspond to the thickness of the slab desired, i.e., a four inch thick slab requires 2xe2x80x3xc3x974xe2x80x3 boards, and a six inch thick slab requires 2xe2x80x3xc3x976xe2x80x3 boards, etc. The boards are temporarily installed with forming stakes about the edges of the slab. The top edge of the boards is then set to the desired slab height (i.e., slab thickness) by laser beam or other appropriate site instrument. The concrete is then poured using the top edge of the perimeter forms as a reference. One disadvantage of this system, however, is that conventional concrete surface finishing machines are only able to finish within about six inches of the slab edge. As a result, the outer borders of the slab must be surface finished manually at considerable time and expense.
The product and process of this invention seeks to perform the same function as the above described traditional concrete form system, but with significantly less labor and greater accuracy. The new process involves basically moving the edges of the slab to a point six to eight inches beyond the actual desired perimeter edge. The unique concrete form in accordance with this invention allows the concrete to be placed on top of the form to a depth of about 1 to about 1xc2xd inches. and six to eight inches beyond the desired perimeter edge of the slab. This extended border that is supported on the form becomes a temporary extended border which is disposable along with form. After the concrete is poured, a conventional surface finish machine is employ ed such to surface finish within about six to eight inches of the temporary extended edge, but at least to the actual desired perimeter edge. After the concrete has sufficiently hardened, a saw cut is made at the actual desired perimeter edge, through the reduced thickness border extension, and the form and along with the border extension are removed. 
The concrete form in accordance with this invention may be made with any suitable but relatively inexpensive material, for example, corrugated laminated cardboard, plastic, metal or the like. The form is substantially box-like in shape, with a laterally outwardly extending flange which facilitates nailing or spiking of the form to the ground to hold the form in place about the perimeter of the slab to be poured. The form has an upper surface flush with an upper edge of one side wall but recessed relative to an upper edge of an opposite side wall to thereby provide a support for the temporary extended border of the slab. In addition, smooth dowel or stakes may be used in conjunction with the form to assist primarily in temporarily holding the form retention to the concrete after the concrete has been poured.
In a preferred arrangement the form may include a rigid foam block which has a height dimension less than a corresponding predetermined thickness for the concrete slab to be poured. The foam block supports on its upper surface, a plastic angle plate including a horizontal portion seated on the upper surface of the foam block, and a vertical edge portion which defines the temporary extended border of the slab. The combined height of the foam block and the vertical plastic edge corresponds to the predetermined thickness of the slab. In this embodiment, the form can be anchored to the crown by one or more spikes driven through the plastic plate and the foam block, with the spike also serving to hold the plastic plate to the foam block.
Accordingly, in its broader aspects, the present invention relates to a concrete form having a first wall defining a height dimension corresponding to a predetermined thickness and a peripheral edge of a concrete slab, and a second wall transverse to the first wall for supporting a temporary extended border portion of the slab, the temporary extended border portion having a thickness less than the predetermined thickness of the slab and such that an upper surface of the slab including the temporary extended border portion is substantially flat and continuous.
In another aspect, the invention relates to a process for pouring and finishing a concrete slab having at least one peripheral edge and a predetermined thickness, the process comprising
a) providing one or more concrete forms in an arrangement defining a periphery of the slab, the form having a recessed top wall providing a support area for a temporary extended border portion of the slab having a thickness less than the predetermined thickness;
b) pouring the concrete within the area defined by the form to a height determined by an upper edge of the form, and so that the temporary extended portion of the slab is supported on the recessed top wall;
c) surface finishing the concrete slab across the top surface thereof, extending outwardly at least to the innermost portion of the temporary extended border portion of the slab; and
d) after the concrete has hardened, removing the from alone with the temporary extended border portion.